This invention relates to complementary metal oxide semiconductor ("CMOS") programmable logic devices, and more particularly, to the use of programmable logic devices as multiplexers.
Integrated circuit devices such as programmable logic arrays typically need large numbers of transfer-devices for such purposes as multiplexing various signals through a single output, circuit control, and data transfer. It is frequently desired for these devices to be programmable so that one integrated circuit can be made to satisfy many different needs. It may also be desired for these transfer-devices to be non-volatile (i.e., to retain the stored information even when the circuit is unpowered).
Heretofore, multiplexers have been implemented using N-channel transfer-devices which are controlled from volatile static-Random Access Memory ("RAM") cells. A static-RAM cell is used to program each individual N-channel transfer-device to allow or prohibit the transfer of data across the device. This implementation requires the use of static-RAM cells, and therefore a static-RAM array, thereby increasing the overall cost and complexity of the programmable logic device.
In view of the foregoing, it is an object of this invention to utilize a non-volatile floating gate structure in such a manner as to reduce or eliminate the need for static-RAM cells in a programmable logic device multiplexer.